The air conditioners of the multi-units installation type are generally used in buildings such as office buildings, tenant buildings and the like for effectively regulating the air conditioning environment of the respective spaces within the buildings. It is estimated that percentage of the air-conditioner power consumption in the total power consumption of the buildings is now in an upward trend.
Meanwhile, in response to the recent demands for energy saving, as described in Japan Laid-open Patent Publication No. JP-A-2004-85087, devices configured to estimate the power consumption of an air conditioner for diagnosing the power consumption have been produced. The power consumption of the air conditioners of the multi-units installation type is greater than that of the air conditioners of a single-unit installation type. Therefore, an energy saving effect is expected to be achieved for the air conditioners of the multi-units installation type through any kind of countermeasure based on the estimation of the power consumption.